It is known in the art of pistons to manufacture integrated pistons from separate head and body portions that are subsequently coupled together in some fashion. Examples of earlier designs that mechanically coupled piston head and body portions together by such means as bolts, threaded studs, etc. can be found in U.S. Pat. No. 4,532,686 to Berchem, U.S. Pat. No. 4,517,930 to Nakano et al, and U.S. Pat. No. 3,877,351 to Barfiss. More current piston designs that are exemplified by U.S. Pat. No. 5,309,818 to Mendes et al. and U.S. Pat. No. 6,651,549 to Zhu et al. rely upon welding piston head and body portions together.
To date, the head and body portions of pistons have been separately forged or cast into piston blanks that are separately machined before being coupled together. This process requires the development of two separate dies or molds and produces a significant amount of waste, as typically the volume of metal used to produce each piston blank has to be quite a bit greater than the actual volume of the blank to compensate for the die or mold design.
The present invention provides a method of making integrated pistons that utilizes a single integrally forged or cast piston blank that is subsequently machined into separate head and body portions.